more stuff

deploy/compose/README.md

@@ -5,6 +5,11 @@ This Compose deployment follows `deploy/k8s/00-config.yaml` and
 of pulling `registry.k6n.net/fancydns`, avoiding a bootstrap dependency on the
 cluster registry DNS.
 
+> **Following the cluster's configuration.** This Compose setup is configured by
+> files and has no link to the cluster's `ClientGroup`, `DNSZone` and other
+> objects. To run a backup resolver that reads them (and keeps serving a saved
+> copy when the cluster is down), see [`../OUTSIDE-CLUSTER.md`](../OUTSIDE-CLUSTER.md).
+
 ## Prepare and start
 
 From the repository root: